Sifting screens used to remove debris such as rock and shale from synthetic drilling muds incorporate layers of woven wire mesh to separate out the debris from the synthetic mud. The screen is vibrated within the shaker and the mesh is subjected to wear from the vibration and the mud and debris. Replacing individual screens as the mesh fails is time consuming and delays the recovery of the mud. To improve the period of time over which any given screen remains operational, the screen is typically divided up into any number of rectangular openings or cells to which the mesh is bonded. If mesh over a given cell fails, this cell can be blocked off leaving the remainder of the screen functioning. This allows the operational life of the screen to be extended, with failure of mesh in one area not compromising the integrity of the remainder of the mesh.
The useful life of the screen needs to be as long as possible. The weight of the screen, the size of the cells and the exposed area of mesh all affect how much drilling mud can be recovered over a given time before the screen needs to be replaced in its entirety.